Tank structure of LNG film tank

Abstract

The application belongs to the technical field of low-temperature liquefied gas storage and transportation, and relates to a tank body structure of an LNG membrane tank, which comprises a main heat insulation module, a shielding membrane and a secondary heat insulation module arranged in the tank body structure from inside to outside in sequence, wherein the shielding membrane is provided with a corrugated part protruding towards the secondary heat insulation module, and the secondary heat insulation module is provided with an avoiding groove accommodating the corrugated part; at least one side of the shielding membrane is provided with a force bearing component from inside to outside in the tank body structure, the force bearing component is provided with a load bearing part corresponding to the avoiding groove, and the load bearing part extends away from the avoiding groove relative to the groove edge of the avoiding groove, so that the load is transferred from the groove edge of the avoiding groove to the load bearing part. The application transfers the load bearing point from the groove edge of the avoiding groove to the load bearing part deviating from the groove edge, eliminates the stress concentration of the groove edge of the avoiding groove, prevents the fatigue damage of the secondary heat insulation module, and further protects the safety of the shielding membrane and the whole tank body structure.

Description

Technical Field

[0001] This invention relates to the field of cryogenic liquefied gas storage and transportation technology, and in particular to the tank structure of LNG membrane tanks. Background Technology

[0002] LNG membrane tanks are cryogenic storage tank structures for storing and transporting liquefied natural gas. The tank body adopts a multi-layer composite structure, which includes a main shielding membrane, a main insulation module, a secondary shielding membrane, and a secondary insulation module from the inside of the tank to the outside. The main insulation module and the secondary insulation module provide support and thermal insulation protection for the shielding membrane on their inner sides, respectively.

[0003] During LNG storage and transportation, temperature fluctuations are drastic. Shielding membranes typically feature corrugated structures with protrusions or recesses to absorb thermal expansion and contraction through corrugation, preventing cracking due to thermal stress. For example, the secondary shielding membrane has corrugated sections protruding towards the secondary insulation module, with corresponding clearance grooves on the secondary insulation module to accommodate these corrugations. These clearance grooves cause the secondary insulation module to lose load support at that location. From a mechanical perspective, the secondary insulation module bodies on either side of the clearance groove form the support area, while the groove opening is equivalent to the mid-span of a simply supported beam with supports at both ends and no support in the middle, where the maximum bending moment is experienced. During long-term operation of the LNG storage tank, alternating loads generated by factors such as sloshing of the internal medium and temperature fluctuations continuously act on the secondary insulation module, causing severe stress concentration at the groove opening edge. This groove opening becomes a weak point in the structure; over long-term operation, the accumulated stress concentration leads to fatigue failure of the secondary insulation module. Summary of the Invention

[0004] Therefore, the present invention provides a tank structure for an LNG membrane tank, which transfers the load-bearing point from the edge of the clearance groove to a load-bearing part that is offset from the groove opening, thereby eliminating stress concentration at the edge of the clearance groove opening, preventing fatigue damage of the secondary insulation module, and thus protecting the safety of the shielding membrane and the entire tank structure.

[0005] To address the aforementioned technical problems, this invention provides a tank structure for an LNG membrane tank, comprising a main insulation module, a shielding membrane, and a secondary insulation module arranged sequentially from the inside of the tank to the outside. The shielding membrane has corrugated portions protruding towards the secondary insulation module, and the secondary insulation module has clearance grooves to accommodate the corrugated portions. From the inside of the tank to the outside, at least one side of the shielding membrane has a load-bearing member. The load-bearing member has a load-bearing portion corresponding to the clearance groove, and the load-bearing portion extends away from the edge of the clearance groove relative to the groove opening, so that the load is transferred from the edge of the clearance groove to the load-bearing portion.

[0006] Preferably, the shielding film is provided with a plurality of corrugated portions, and the secondary insulation module is provided with a relief groove corresponding to each of the corrugated portions.

[0007] Preferably, the load-bearing component includes a secondary load-bearing component; from the inside of the tank to the outside of the tank, the secondary load-bearing component is disposed between the shielding film and the secondary insulation module; at least one of the clearance grooves on the secondary load-bearing component is provided with a first load-bearing part.

[0008] Preferably, the load-bearing component includes a main side load-bearing component; from the inside of the tank to the outside of the tank, the main side load-bearing component is disposed between the main insulation module and the shielding film; at least one second load-bearing part is provided on the main side load-bearing component corresponding to one of the clearance grooves.

[0009] Preferably, the load-bearing component includes a secondary load-bearing component and a primary load-bearing component; from the inside of the tank to the outside of the tank, the primary insulation module, the primary load-bearing component, the shielding film, the secondary load-bearing component, and the secondary insulation module are stacked sequentially; at least a corresponding portion of the clearance groove on the secondary load-bearing component is provided with a first load-bearing part, and at least a corresponding portion of the clearance groove on the primary load-bearing component is provided with a second load-bearing part; wherein, the first load-bearing part and the second load-bearing part correspond to different clearance grooves.

[0010] Preferably, the distance D between the load-bearing edge of the load-bearing part and the groove edge of the relief groove in a direction parallel to the shielding film is 10~15mm.

[0011] Preferably, the distance D between the load-bearing edge of the load-bearing part and the groove edge of the relief groove in a direction parallel to the shielding film is 12mm.

[0012] Preferably, the load-bearing portion is a step that extends away from the groove edge relative to the groove opening.

[0013] Preferably, the step includes a first step surface and a second step surface, the first step surface being parallel to the shielding film and the second step surface being perpendicular to the shielding film.

[0014] Preferably, the gap between the corrugated portion and the clearance groove is filled with resin adhesive; or / and the inner cavity of the corrugated portion is filled with thermal insulation cotton.

[0015] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0016] The LNG membrane tank structure of the present invention has a load-bearing part on the load-bearing component that is offset away from the edge of the relief groove. This transfers the actual load-bearing part from the edge of the relief groove to the load-bearing part offset from the groove. From a mechanical point of view, this is equivalent to moving the load-bearing point from the mid-span region of a simply supported beam to the support region, significantly reducing the bending moment and stress at the edge of the relief groove, effectively eliminating stress concentration at the groove edge, thereby preventing fatigue failure of the secondary insulation module and effectively protecting the safety of the shielding membrane and the entire tank structure. Attached Figure Description

[0017] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0018] Figure 1 This is a three-dimensional schematic diagram of the LNG membrane tank structure in the first embodiment;

[0019] Figure 2 yes Figure 1 The diagram shows the assembly of the secondary load-bearing components and secondary insulation modules in the tank structure shown.

[0020] Figure 3 yes Figure 2 A magnified view of part A shown in the diagram;

[0021] Figure 4 This is a three-dimensional schematic diagram of the LNG membrane tank structure in the second embodiment;

[0022] Figure 5 yes Figure 1 The front view of the LNG membrane tank structure shown;

[0023] Figure 6 yes Figure 4 A schematic diagram of the assembly of the main load-bearing components and the main insulation module in the tank structure shown;

[0024] Figure 7 yes Figure 6 A magnified view of part B shown.

[0025] 2. Main insulation module; 4. Shielding film; 41. Corrugated section; 6. Secondary insulation module; 61. Clearance groove; 81. Secondary side load-bearing component; 811. First load-bearing part; 82. Main side load-bearing component; 821. Second load-bearing part; 83. First step surface; 84. Second step surface; 10. Resin adhesive; 12. Thermal insulation cotton. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0027] Reference Figure 1 As shown, this embodiment of the invention proposes a tank structure for an LNG membrane tank, including a main insulation module 2, a shielding film 4, and a secondary insulation module 6 arranged sequentially from the inside of the tank to the outside; the shielding film 4 between the main insulation module 2 and the secondary insulation module 6 is the secondary shielding layer of the LNG membrane tank; the main shielding film is arranged inside the main insulation module 2 and is in direct contact with the medium inside the tank.

[0028] Understandably, the shielding membrane 4 is made of a metal film plate structure, such as stainless steel, aluminum alloy, or Invar alloy. The shielding membrane 4 is provided with corrugated portions 41 extending laterally and / or longitudinally, which are used to absorb shrinkage deformation caused by temperature changes and bending deformation of the hull beam in waves.

[0029] It is understood that the corrugated portion 41 on the shielding film 4 protrudes from its flat portion toward the inside or outside of the tank. In the embodiment of the present invention, the shielding film 4 is provided with a corrugated portion 41 protruding toward the secondary insulation module 6; correspondingly, the secondary insulation module 6 is provided with a relief groove 61 to accommodate the corrugated portion 41.

[0030] It is understandable that multiple corrugated portions 41 can be arranged on the shielding film 4 according to actual usage needs. When the corrugated portion 41 extends laterally, multiple corrugated portions are arranged sequentially at intervals along the longitudinal direction; or, when the corrugated portion 41 extends longitudinally, multiple corrugated portions are arranged sequentially at intervals along the transverse direction.

[0031] Correspondingly, when multiple corrugated portions 41 are excluded on the shielding film 4, a relief groove 61 is provided on the secondary insulation module 6 for each corrugated portion 41.

[0032] The presence of the clearance groove 61 causes the secondary insulation module 6 to lose load support at that location. From a mechanical perspective, the secondary insulation modules 6 on both sides of the clearance groove 61 form the support area, while the opening of the clearance groove 61 is equivalent to the mid-span region of a simply supported beam that is supported at both ends but unsupported in the middle. The simply supported beam experiences the greatest bending moment in the mid-span region, thus resulting in severe stress concentration at the edge of the clearance groove 61. During the long-term operation of the LNG storage tank, alternating loads generated by factors such as sloshing of the internal medium and temperature fluctuations continuously act on the secondary insulation module 6, making the edge of the clearance groove 61 a structurally weak point, prone to fatigue failure under long-term operation.

[0033] To address this problem, this embodiment of the invention provides a load-bearing member on at least one side of the shielding film 4, and a load-bearing portion on the load-bearing member corresponding to the relief groove 61. The load-bearing portion extends away from the edge of the relief groove 61, thereby transferring the actual load-bearing area from the edge of the relief groove 61 to the load-bearing portion offset from the groove. From a mechanical perspective, this is equivalent to moving the load-bearing point from the mid-span region of the simply supported beam towards the supporting region, significantly reducing the bending moment and stress at the edge of the relief groove 61.

[0034] like Figures 1-3 As shown, in one embodiment of the present invention, the load-bearing component includes a secondary load-bearing component 81, which is disposed between the shielding film 4 and the secondary insulation module 6 in the direction from inside the tank to outside the tank. It can be understood that the main insulation module 2, the secondary load-bearing component 81, the shielding film 4 and the secondary insulation module 6 are stacked sequentially in the direction from inside the tank to outside the tank.

[0035] For example, the secondary load-bearing member 81 is a plate-shaped member disposed between the shielding film 4 and the secondary insulation module 6, made of plywood, and has high strength and rigidity.

[0036] At least one first load-bearing part 811 is provided on the secondary load-bearing member 81 corresponding to an avoidance groove 61.

[0037] Specifically, a break is made on the secondary load-bearing member 81 at the position corresponding to the relief groove 61; since the shielding film 4 is located above the secondary load-bearing member 81, the break penetrates the secondary load-bearing member 81 in the thickness direction, allowing the corrugated part 41 to pass through the break and enter the relief groove 61.

[0038] The secondary load-bearing member 81 extends from the edge of the fracture towards the direction away from the relief groove 61 to form a first load-bearing portion 811. Specifically, the first load-bearing portion 811 is a step extending away from the groove edge of the relief groove 61 relative to the groove edge. When a load is applied to the secondary insulation module 6, the load is no longer concentrated at the groove edge of the relief groove 61, but is received and transferred through the first load-bearing portion 811 of the secondary load-bearing member 81. Since the first load-bearing portion 811 extends away from the groove edge of the relief groove 61 relative to the groove edge, the load-bearing point moves from the mid-span region of the simply supported beam towards the support region, thereby significantly reducing the bending moment and stress at the groove edge of the relief groove 61 and effectively eliminating the stress concentration phenomenon at the groove edge.

[0039] It is understandable that a first load-bearing part 811 can be provided for each relief groove 61 to protect the groove edges of all relief grooves 61 in the entire tank structure and avoid fatigue damage caused by local stress concentration.

[0040] In this embodiment, the secondary load-bearing member 81 receives and transmits the load from the outside of the tank, so that the load no longer acts directly on the edge of the relief groove 61 of the secondary insulation module 6, but is dispersed and transmitted through the secondary load-bearing member 81, thereby reducing the stress level of the secondary insulation module 6.

[0041] Reference Figures 4-7 As shown, in another embodiment of the present invention, the load-bearing component includes a main side load-bearing component 82, which is disposed between the main insulation module 2 and the shielding film 4 in the direction from inside the tank to outside the tank. It can be understood that the main insulation module 2, the main side load-bearing component 82, the shielding film 4 and the secondary insulation module 6 are stacked sequentially in the direction from inside the tank to outside the tank.

[0042] For example, the main load-bearing member 82 is a plate-shaped member disposed between the main insulation module 2 and the shielding film 4, made of plywood, and has high strength and rigidity.

[0043] At least one clearance groove 61 is provided on the main side load-bearing member 82 to provide a second load-bearing part 821.

[0044] Specifically, a notch is provided on the side of the main load-bearing member 82 facing the shielding film 4 and corresponding to the position of the clearance groove 61. Since the shielding film 4 is located below the main load-bearing member 82, it does not need to allow the corrugated part 41 to pass through. The notch is a blind notch with the surface of the main load-bearing member 82 facing the shielding film 4 recessed inward. The secondary load-bearing member 81 extends from the notch in a direction away from the clearance groove 61 to form a second load-bearing part 821. Similarly, when a load is applied to the secondary insulation module 6, the load is no longer concentrated at the edge of the clearance groove 61, but is received and transferred through the second load-bearing part 821 of the main load-bearing member 82. Since the second load-bearing part 821 extends away from the clearance groove 61 relative to the edge of the clearance groove 61, the load receiving point moves from the mid-span area of ​​the simply supported beam to the support area, thereby significantly reducing the bending moment and stress at the edge of the clearance groove 61 and effectively eliminating the stress concentration phenomenon at the edge of the groove.

[0045] In another embodiment of the present invention, the load-bearing components include a secondary load-bearing component 81 and a primary load-bearing component 82; from the inside of the tank to the outside, the primary insulation module 2, the primary load-bearing component 82, the shielding film 4, the secondary load-bearing component 81, and the secondary insulation module 6 are stacked sequentially. At least a corresponding portion of the clearance groove 61 on the secondary load-bearing component 81 is provided with a first load-bearing portion 811, and at least a corresponding portion of the clearance groove 61 on the primary load-bearing component 82 is provided with a second load-bearing portion 821. The first load-bearing portion 811 and the second load-bearing portion 821 correspond to different clearance grooves 61.

[0046] Specifically, in this embodiment, not every clearance groove 61 is simultaneously supported by the first load-bearing part 811 and the second load-bearing part 821. Instead, the multiple clearance grooves 61 are divided into two groups: one group is supported by the first load-bearing part 811 on the secondary side load-bearing member 81, and the other group is supported by the second load-bearing part 821 on the main side load-bearing member 82. The advantage of this arrangement is that, based on the actual load distribution in different areas of the tank, the load-bearing member on the inner or outer side of the tank can be flexibly selected to support the load on a specific clearance groove 61, achieving differentiated load distribution. Simultaneously, it avoids the structural complexity and assembly difficulties caused by simultaneously setting two load-bearing parts at the same clearance groove 61. Those skilled in the art can allocate all clearance grooves 61 to be supported by the first load-bearing part 811, or by the second load-bearing part 821, or partially by the first load-bearing part 811 and partially by the second load-bearing part 821, all of which fall within the scope of protection of this invention.

[0047] In the embodiments of the present invention, on the one hand, the main load-bearing member 82 receives and transmits the load from the inside of the tank, and works in conjunction with the load-bearing member set on the outside of the tank to further disperse the load at the edge of the relief groove 61, thereby improving the overall load-bearing capacity and fatigue life of the structure.

[0048] On the other hand, the first load-bearing part 811 and the second load-bearing part 821 correspond to different relief grooves 61. According to the actual load distribution in different areas of the tank, the load-bearing components on the inside or outside of the tank can be flexibly selected to bear the load on a specific relief groove 61, so as to achieve differentiated load distribution, while avoiding the structural complexity and assembly difficulties caused by setting two load-bearing parts at the same relief groove 61.

[0049] In this embodiment, the distance D between the load-bearing edge of the load-bearing portion and the groove edge of the relief groove 61 in a direction parallel to the shielding film 4 is 10 to 15 mm. Preferably, the distance D is 12 mm.

[0050] Specifically, the load-bearing edge of the load-bearing part refers to the edge on the load-bearing part that actually bears and transmits the load. The groove edge of the relief groove 61 refers to the opening edge of the relief groove 61 on the surface of the secondary insulation module 6. The distance D is the spacing between the two in the direction parallel to the shielding film 4. The value of the distance D needs to take into account two factors: on the one hand, the distance D should not be too small, otherwise the load-bearing part and the groove edge of the relief groove 61 will be too close, and the load-bearing point will still be close to the mid-span area of ​​the simply supported beam, which will not effectively reduce the bending moment and stress at the groove edge; on the other hand, the distance D should not be too large, otherwise the load-bearing part will be too far away from the relief groove 61, the load transmission path will be too long, which may lead to the size of the load-bearing component being too large, increasing the amount of material used and the manufacturing cost, and may also affect the overall structural layout of the tank. Through mechanical analysis and engineering practice, it has been verified that when the distance D is 10 to 15 mm, the load-bearing point can be effectively moved from the mid-span region of the simply supported beam to the supporting region, significantly reducing the bending moment and stress at the edge of the relief groove 61, while also considering structural compactness and manufacturing cost. More preferably, a distance D of 12 mm yields the best overall effect.

[0051] In this embodiment, the load-bearing portion is a step extending away from the edge of the relief groove 61. The step includes a first step surface 83 and a second step surface 84, the first step surface 83 being parallel to the shielding film 4 and the second step surface 84 being perpendicular to the shielding film 4.

[0052] Specifically, the edges of the aforementioned breaks or notches (hereinafter collectively referred to as "notches") are designed with stepped structures to form load-bearing portions. The first step surface 83 of the step is parallel to the shielding film 4, forming the load-bearing surface that actually bears the load; the second step surface 84 of the step is perpendicular to the shielding film 4, forming a transition surface between the first step surface 83 and the inner wall of the notch. When a load is applied to the secondary insulation module 6, the load is received and transferred through the first step surface 83, rather than through the edge of the relief groove 61. The second step surface 84 connects the first step surface 83 to the inner wall of the notch, forming a stepped transition structure between the load-bearing portion and the notch. The stepped structure is easy to process and can be formed on the load-bearing component by machining or mold forming, and the accuracy is easy to ensure.

[0053] Furthermore, in this embodiment, the gap between the corrugated portion 41 and the relief groove 61 is filled with resin adhesive 10; and / or the inner cavity of the corrugated portion 41 is filled with thermal insulation cotton 12. The resin adhesive 10 is used to fill the gap between the corrugated portion 41 and the relief groove 61, preventing the corrugated portion 41 from shaking within the relief groove 61, while also providing a certain degree of sealing and heat insulation. Exemplarily, the thermal insulation cotton 12 is preferably made of glass wool, used to fill the inner cavity of the corrugated portion 41, further improving the heat insulation performance of the corrugated portion 41 area and reducing cold loss.

[0054] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. The tank structure of an LNG membrane tank includes a main insulation module, a shielding membrane, and a secondary insulation module arranged sequentially from the inside of the tank to the outside; the shielding membrane has corrugated portions protruding towards the secondary insulation module, and the secondary insulation module has clearance grooves to accommodate the corrugated portions, characterized in that... From the inside of the tank to the outside of the tank, at least one side of the shielding film is provided with a load-bearing member; the load-bearing member is provided with a load-bearing part corresponding to the relief groove, and the load-bearing part extends away from the relief groove relative to the groove edge, so that the load is transferred from the groove edge of the relief groove to the load-bearing part.

2. The tank structure of the LNG membrane tank according to claim 1, characterized in that... The shielding film is provided with multiple corrugated sections, and the secondary insulation module is provided with a relief groove corresponding to each corrugated section.

3. The tank structure of the LNG membrane tank according to claim 2, characterized in that... The load-bearing component includes a secondary load-bearing component; from the inside of the tank to the outside of the tank, the secondary load-bearing component is disposed between the shielding film and the secondary insulation module; at least one of the clearance grooves on the secondary load-bearing component is provided with a first load-bearing part.

4. The tank structure of the LNG membrane tank according to claim 2, characterized in that... The load-bearing component includes a main side load-bearing component; from the inside of the tank to the outside of the tank, the main side load-bearing component is disposed between the main insulation module and the shielding film; at least one second load-bearing part is provided on the main side load-bearing component corresponding to one of the clearance grooves.

5. The tank structure of the LNG membrane tank according to claim 2, characterized in that... The load-bearing components include secondary load-bearing components and primary load-bearing components; from the inside of the tank to the outside of the tank, the primary insulation module, the primary load-bearing component, the shielding film, the secondary load-bearing component, and the secondary insulation module are stacked in sequence; at least a corresponding portion of the clearance groove on the secondary load-bearing component is provided with a first load-bearing part, and at least a corresponding portion of the clearance groove on the primary load-bearing component is provided with a second load-bearing part; wherein, the first load-bearing part and the second load-bearing part correspond to different clearance grooves.

6. The tank structure of the LNG membrane tank according to any one of claims 1-5, characterized in that... The distance D between the load-bearing edge of the load-bearing part and the groove edge of the relief groove in a direction parallel to the shielding film is 10~15mm.

7. The tank structure of the LNG membrane tank according to claim 6, characterized in that... The distance D between the load-bearing edge of the load-bearing part and the groove edge of the relief groove in a direction parallel to the shielding film is 12mm.

8. The tank structure of the LNG membrane tank according to claim 1, characterized in that... The load-bearing portion is a step that extends away from the clearance groove relative to the groove edge.

9. The tank structure of the LNG membrane tank according to claim 8, characterized in that... The step includes a first step surface and a second step surface, the first step surface being parallel to the shielding film and the second step surface being perpendicular to the shielding film.

10. The tank structure of the LNG membrane tank according to claim 1, characterized in that... The gap between the corrugated part and the clearance groove is filled with resin glue; or / and the inner cavity of the corrugated part is filled with thermal insulation cotton.

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